Reciprocating sander



Jan. 27, 1959 L. 1.. LYON RECIPROCATING SANDER afar 128/ Ma. 1.

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Lacs/1v Lye, INVENTOR.

4rrapug4 L. L. LYON RECIPROCATING SANDER Jan. 27, 1959.

3 Sheets-Sheet 3 Filed Jan. 25. 1957 HIHHHHHHHIIHI.

llll-lal M m l L M w United States Patent() RECIPROCATING SANDER Luc'ein L. Lyon, Huntington Park, Califi, assignor to Ralph W. Walsh Application January 23,1957, Serial No. 635,706

6 Claims. (Cl- 51'170) This invention relates to improved sanding devices of the type including a handle section to be held by a user, and a shoe section which is power reciprocated relative to the handle section and carries a sheet of sanding paper or other abrasive sheet material for acting on a work surface.

In sanders of this general type, it is frequently desirable to design the sander to discharge a selected fluidon to the work surface during a sanding operation, to assist in treating or cleaning that surface. Certain features of the present invention have to do with improved means for thus discharging such a fluid onto the work surface. In prior sanders, any such fiuid which has been utilized has been fed onto the work at one of the sides of the sander, that is, at a location offset from the sander transversely of its axis of reciprocation. As a result, the user has :had to move the sander transversely of its direction of reciprocation to reach the spot most recently contacted by the fluid, which movement often produces angular sanding marks or scratches on the work. In the present device, this disadvantage is overcome by discharging the fluid onto the work at a location beyond the sander axially of the device, and preferably directly in front of the sander, so that the device may be easily moved forwardly, without transverse shifting, onto the work area most recently contacted by the discharged fluid.

Preferably, the sander is designed to selectively discharge either water or air onto the work, the water being to wet down the work surface, and the air being to blow abraded particles and the like off of the surface. Certain particular features of theinvention have to do with the valve arrangement which is utilized to control the discharge and flow of these fluids. When air is to be discharged, it may be taken as a branch stream from a main flow of air leading to an air actuated piston and cylinder mechanism for driving the reciprocating shoe. When water or another liquid is to be used on the work, a suitable water supply line may be connected to a separate water inlet connection on the sander, and a special valve in the sander may then be closed to shut off the flow of air to the work. A second valve is provided for starting and stopping the discharging of the selected fluid, whether it be water or air, onto the work, and a third and separately operated valve controls the delivery of air to the actuating cylinder. The separate air and water inlet lines may connect into the back end of the handle, with the first of the three discussed valves also desirably being at that location. The second valve may be controlled by a push button actuable from the front of the handle, while the third valve is actuable by an element which overlies the top of the handle.

Additional features of the invention reside in the manner in which a counterweight, for counterbalancing the movements of the piston, is mounted and driven by a rocker arm structure. Of particular importance is the mounting of this counterweight and rocker arm in a manner such that none of the main driving force exerted by the piston on the shoe is transmitted through the counterweight or rocker arm mechanism. Also important is a unique manner of lubricating the rocker arm .as well as Patented Jan. 27,1959

the piston and other-moving parts of the apparatus, by introducing a lubricant mist into the compressed air being fed to the piston, and then directing that air, as it discharges from the piston and cylinder, onto the rocker arm mechanism. The counterweight may then contain grooves or recesses so positioned as to accumulate the lubricant and feed it to certain of the pivot points in the mechanism.

The present invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawings, in which:

Fig. 1 is a perspective view of a sanding device constructed in accordance with the invention;

Fig. 2 is a vertical section taken essentially on line 22 of Fig. 1;

Fig. 3 is a plan view of the device shown in Figs. 1 and 2, with the top control element or plate broken away to show the interior of the casting just beneath that plate;

Fig. 4 is a vertical section taken on line 4-4 of Fig. 3;

Fig. 5 is afragmentary essentially vertical section taken on line 5-5 of Fig. 4;

Fig. 6 is an enlarged fragmentary vertical section taken on line 6-6 of Fig. 2;

Fig. 7 is an enlarged fragmentary vertical section taken on line 7-7 of Fig. 4;

Fig. 8 is an enlarged fragmentary horizontal section taken on line 8--8 of Fig. 4;

.Fig. 9 is an enlarged fragmentary vertical section taken on line ,9-9 of Fig. 3;

Fig. 10 is an enlarged fragmentary exploded view showing the parts through which the used air from the piston and cylinder mechanism is discharged;

Fig. 11 is a perspective view of the upper portion of the handle section of the device, with the top actuating or control member swing upwardly to show the parts received therebeneath;

Fig. 12 is an enlarged fragmentary section taken on line 12'12 of Fig. 2;

Fig. 13 is a fragmentary section showing the device with a plug closing the water inlet passage, so that fair rather than water may be discharged onto the work :surface; and

Fig. 14 is an exploded perspective view of the cylinder block and associated parts.

Referring first to Fig. 1, I have shown in the drawings a sander 10 constructed in accordance with the invention, and including an upper handle section 11 which is held in thehand of the user, and a lower relatively reciprocating shoe section 12 which carries the sanding sheet 13. The lower shoe section 1 2 is reciprocated relative to upper handle section 11 by means of a :piston and cylinder mechanism 14 contained wi-thinsections .11 and 12, with actuating pressure fluid, preferably :compressed air, being fed to the mechanism 14 through a flexible supply line or hose 15. The supply of compressed air to the piston and cylinder mechanism 14 is controlled by manual depression of an upper actuating member 16 relative to handle section 11. If desired, a fluid may be discharged onto the work surface during a sanding operation, through a tube 17. This fluid which is supplied through line 15, .or another fluid {preferably water) fed to the apparatus through a second supply line 18. Lines 15 and 18 are-connected .into the back end of section 11 of the device, while the discharge of fluid onto the work through line 17 may be controlled by inward manual actuation of a push-button 19 located at the forward end of section 11. For minimizing the tendency to reciprocate handle section 11, there may be provided within the device a counterweight 20 (see Fig. 2), which reciprocates ain opposition'to the reciprocation ofshoe 12.

,mechanism is contained, this upper portion being defined by a pair of essentially vertical side walls 24, and a pair of essentially vertical but preferably slightly upwardly converging end walls 25. At the lower extremities of walls 24 and 25, member 21 has a horizontal peripheral flange 26, to which the lower cushion 22 is attached, as by ,four corner screws 27 extending downwardly through openings in flange 26 and threadedly connecting into a metal reinforcing plate 28 embedded in the upper portion of cushion 22. The cushion 22 may contain a series of recesses 29 extending into the cushion from its opposite sides, torincrease its resiliency.

The sheet of sand paper 13 extends along the under side of cushion 22, and extends upwardly at the opposite ends of the cushion for releasable connection thereto by apair of essentially conventional swinging clamps 30.. .These clamps 30 may be mounted by pins 31 to lugs 32 of member 21 for swinging movement about the spaced parallel axes of the two pins 31 relative to member 21. The lower clamping portions 33 of clamps 30 are-yieldingly held by springs. 34 against the up-turned wall 48 of recess 45 terminates at 49, to provide an opening 50 at that location providing access between the upper side and undersideof handle 11 (when element 16 is removed). Also, toward the rear of handle 11, there may be a pair of openings 51 and 52 providing access between the upper and underside'of handle 11. The staupward opening movement beyond its position of Figs. 1 and 2 by means of a leaf spring latch element 56, which is attached at 57 to the inner side of flange 46, and which has a turned edge 58 adapted to be received beneath a coacti'ng horizontal portion 59 of cover section 11 to limit upward movement of the forward end of element 16.

When it is desired to open element 16 upwardly to make 1 tab 58 may be pressed rearwardly by the tool and then ends of sand paper sheet 13, to tightly clamp that sheet against toothed surfaces 35 formed on lugs 36 of members 21. Thus, the sheet 13 is very tightly held by clamps inthe illustrated position of attachment to shoe 12. The upper rigid handle section 11 of the device extends across the upper side of portion 23 of shoe 12, and extends'downwardly about the sides and ends of that portion 21, with sufficient clearance at the ends of section 11 to allow for reciprocation of shoe 12 relative to section 11. The two side walls 37 of section 11 extend vertically and generally parallel at the opposite sides of portion 23 of part 21, and the opposite end walls 38 of section 11 also extend vertically and generally parallel .to one another. At the top of section 11, the side walls 37 and the forward one of the endwalls 38 (the righthand end wall 38 in Fig. 2)v curve progressively inwardly, as at 39 in Fig. 2, to present a rounded contour adapted to fit and be easily held by the hand of a user. At the back of the sander, the upper rigid handle section '11 has a rearwardly projecting portion 40, containing two rearwardly opening passages 41 and 42 into which the end fittings 43 and 44 of hoses 15 and 18 respectively are threadedly connected.

The upper portion of handle 11, that is, the portion which extends across the top of portion 23 of shoe 12, is-

recessed downwardly at 45 to receive the previously mentioned control element 16. This part 16 may be formed of rigid sheet metal, which extends approximately horizontally across the upper side of handle 11, and is peripherally turned downwardly at 46 along the opposite sides and forward end of recess 45, to form a peripheral flange at 46 which is received just within the confines of recess 45. At its rear end, the actuating or control member 16 is mounted by a hinge 47 for limited swinging movement downwardly from the upwardly projecting position of Figs. 1 and 2 to a depressed position in which the horizontal portion of member 16 is substantially flush with the upper surface of handle 11. As will be apparent, the control element 16 is automatically depressed to its lowered position when a user grasps handlell and then presses the palm of his hand downwardly against element 16 in using the device.

The configuration of handle 11 within its upper recess 45 is illustrated in Fig. 11. As seen in that figure, the bottom of recess 45 is defined over the most of its area by a wall 48, which is offset sufiiciently beneath part 16 to .allow the desired limited vertical movement of part 16. 1 Toward the forward end of handle 11, the bottom repairs or for any other reason, element 56 may be released by inserting a screw driver or other tool downwardly through the narrow space 60 between flange 46 and portion 59 (and with element 16 depressed), so that held in that retracted position, against the resilience of the material of element 56, as part 16 is'swung upwardly beyond portion 59. of the handle. As best seen in Fig. 3, the recess 45 which receives element 16 is defined by' a 3 wall which curves progressively about the forward end of element 16, with the latter and its flange 46 having essentially'the same curving generally U-shaped configuration.

The piston and cylinder mechanism 14 includes a cylini der 61 rigidly attached to the underside of top wall 48 of 1 tially close the opposite ends of the main cylinder block 61. These end plates 64 may be attached to cylinder 61 in any suitable way, as by a number of screws represented at 65, with suitable gaskets or other sealing material of course being provided between the end plates and cylinder block 61. The cylinder 61 and its end plates 64 are rigidly attached to the underside of wall 48 by a number of screws 66 (see Fig. 3).

The piston 62 is rigidly attached to a piston rod 67, which projects in opposite axial directions from the piston, and extends through sealed openings 68 in end plates 64. At its left end, as seen in Figs. 2 and 4, piston rod 67 1 for reception of a rocker arm driving assembly 72 axially between the forward end 73 of rod 67 and the front wall 25 of shoe 12. Referring to Fig. 2, this assembly 72 includes an annular sleeve 74 having a flange 75 at one end abutting against the end 73 of rod 67. A nut 76 is threadedly connected onto the opposite end of sleeve 74, to

' tightly clamp between flange 75 and nut 76 a rigid ring 77 and two intermediate washers 78. A screw 79 extends through forward wall 25 and sleeve 74, and threadedly connects into the forward end of piston rod 67 at 80, to rigidly secure assembly 72 and the forward end of the piston rod in fixed relation to wall 25. Thus, the piston and its rod 67 are rigidly attached to shoe 12 and act to very positively reciprocate that shoe axially of cylinder 61 relative to handle 11.

The counterweight 20 extends horizontally across the underside of cylinder 61, and is formed of a material and of a size capable of counterbalancing the reciprocations of the shoe 12. Specifically, weight 20 may be formed of a cast metal. The counterweight is spaced from both cylinder 61 and cushion 22, to be freely 'movable relative thereto, and is driven by piston and cylinder mechanism 14 through a rocker arm 81. This rocker arm 81 has an upper bifurcated yoke portion (see Fig. 5), whose two arms are pivotally connected to opposite sides of the previously mentioned rigid ring 77 of assembly 72 by a pair of axially aligned pivot pins 82. These pivot pins may be fixed relative to the rocker arm 81 by set screws 83, and may be pivotally movable within openings 84 and ring 77, to thus connect rocker arm 81 to piston rod 67 for relative pivotal movement about an axis extend ing directly transversely of and through the axis of rod 67.

At its lower end, rocker arm 81 is pivotally connected by a" horizontal pin 85 to a forward end of counterweight 20. Vertically between 'pin 85 and the upper pins 82, the rocker arm is pivotally connected by a pin 86 to a forwardly projecting lug 87 carried by end plate 64 of cylinder 61. At its rear end, counterweight 20 is pivotally connected by a pin 88 to the lower end of a link 89, whose upper end is pivotally connected by a pin 90 to a lug 91 projecting rearwardly from the rear end plate 64 of the cylinder. As will be apparent, the pivotal connections at 82, 85, 86, 88 and 90 all have parallel horizontal axes. Also, the spacing of axes 85, 86, 88 and 90 is such as to form a parallelogram between these four axes, thus mounting counterweight 20 for reciprocation beneath cylinder 61. The connection formed by rocker arm .81 acts to move counterweight 20 rearwardly relative to handie 11 when shoe 12 is actuated forwardly, and vice versa.

The handle and shoe sections are further guided for .the desired reciprocal movement by means of four rollers 92, which are rotatably mounted to opposite'sides of the cylinder end walls 64. These rollers 92 may be formed of a tough resinous material, such as a phenolic, and may be mounted to the end walls 64 by headed stub shafts or pins 93 rigidly attached to walls 64 (see Fig. 12). The four rollers 92 are rotatable relative to cylinder 61 about two spaced parallel transverse axes 94 and 95, which lie in a common horizontal plane. Rollers 9 2 ride on a pair of horizontally extending tracks 96 which extend along and are rigidly secured to the upper edges of side walls 24 of shoe 12. Thus, the engagement of rollers 92 with hardened tracks 96 acts to prevent cylinder 61 and handle 11 from turning about the axis of pi'ston rod 67 relative to shoe section 12.

Referring now to Fig. 4, the compressed air or other pressure fluid from hose flows forwardly from the communicating threaded passage 41 through a reduced diameter passage 97 in handle 11, to flow upwardly past annular seat 98 coacting with a vertically movable element 99 which is actuated by the previously discussed control member 16. Element 99 has an upper actuating end portion 100, which is engaged against the underside of control member '16, with a fluid seal being provided by a ring 101. Valve element 99 is yieldin'gly urged upwardly by a coil spring 102, which may be held in position by a bottom retaining screw 103.

When element 16 and valve 99 are depressed, air may pass through valve seat 98 and into av passage 104 extending forwardly and then downwardly through two passages 105 in part 11, and communicating passages in part 61 and a tubular liner or sleeve 107, within which sleeve a spool type slide valve 108 is movable axially of piston 62. From the interior of sleeve 107, compressed air flows to the opposite ends of cylinder 61 through a pair of passages 109 and. .110 formed in the sleeve and cylinder. Exhaust ai r leaves sleeve 107 through two upper passages 211 formed in sleeve 107 and part 61, whichv passages both lead into a passage 111 formed in the top wall portion 48 of handle section 11. This passage 11.1 extends first upwardly into wall 48, and then forwardly at 1'11'aalong the upper side -0t wall 48, to discharge the air from the cylinder structure at 112. I'

The slide valve 108 is controlled by a parallel elongated axially extending slide type pilot valve 208, which is slidable within a sleeve 207 in the cylinder structure and projects from oppositeends of cylinder member 61. This valve 208 carries at its opposite ends a pair of rubber cushion elements 113, which are cup-shaped and disposed about the ends of valve 208, and bear against end walls 25 of the shoe structure. The rubber cups 113 not to take up all play between slide valve 208 and end walls 25, to thus positively reciprocate valve 208 in exact correspondence with the movement of shoe 11 relative to cylinder 61. The various annular grooves lands of pilot valve 208 are so designed as to alternately admit compressed air to the opposite ends of sleeve 107, in accordance with reciprocal movements of the piston, to thus reciprocate main valve 108 axially within sleeve 107. Valve 108 in turn alternately admits compressed air to the opposite ends of cylinder 61 through passages 109 and 110, and discharges air from each of these ends of the cylinder through passage 109 or 110, sleeve 107 "and passages 211 and 111 when air is being admitted to the other end. The valves alternate the air supply and discharge connections in such timed relation to the movement of piston 62 as to cause continued reciprocation of that piston and shoe 12 relative to handle 11 and cylinder 61 as. long as element 16 and valve 99 are depressed.

The parts of course contain suitable passages for delivering air to and from sleeve 207, in any manner capable of eifecting the desired pilot valve action. These .pas-

sages may typically be formed in the opposed or abutting surfaces of parts 61, 48, and 64. Specifically, air may flow from passages through a pair of passages or grooves 206 formed in the underside of wall 48 (see Fig.

l4) and leading to a pair of passages 209, formed in parts 61 and 207, which passages lead :air to the interior of sleeve 207. From the opposite end portions of sleeve 207, air is alternately passed through a pair of side slits'3'00 in the sleeve into a pair of passages 311 which are formed in the inner surfaces of parts 64 and communicate with opposite ends of sleeve 107. Air discharged from the opposite ends of sleeve 107 through passages or grooves 210 in members 64 (alternately) fiowsthrough a pair of angular grooves 212 formed in the upper surface of parls 61, and flows downwardly from the inner ends of those grooves through passages 301 into the central portion of sleeve 207. The valve 208 then controls the flow of discharge air from passages 301 to a discharge passage 212 which leads to the outside of the cylinder structure for discharge to atmosphere. The passages 206 may cross over passages 212, but :are isolated therefrom by a gasket 213 received between parts 61 and 48 and containing apertures at the proper locations for passing air to and from the opposite ends of passages 206, and for passing discharge air upwardly from passage 211 to passage 111.

Desirably, the compressed air fed to the sander through line 15 contains a fine mist of oil, and for this purpose is fed through a conventional lubricator unit represented at 314 in Fig. 1. This fine mist of oil acts to efiectively lubricate the piston valves and cylinder, and also may be utilized after leaving the cylinder to lubricate the various moving parts associated with the counterweight driving assembly. For this latter purpose, I prefer to provide at the top of wall 48 a deflector element 114, which may be formed of sheet metal bent to ,the illustrated configuration, and disposed across and closing the upper side of passage 111 (including its forwardly extending portion 111a). This .plate 114 may be attached to the top wall of 48 in any suitable manner, as by upsetting the material of wall 48 at a number of locations 115 to extend a short distance over plate 114. As seen in Fig. 10, plate 114 may contain an opening 215 through which one of the previously mentioned s'crews6'6 may pass for connecting {parts 48 and .61,

' 88 respectively, to feed the lubricant thereto.

As will be apparent from Figs. 4 and 10, plate 114 con- 7 manner 'suchthat the air must discharge only at the forward end 112 of passage 111. At that point, the forward end of plate 114 is turned angularly downwardly 'at 114a, across the path of the forwardly moving air from passage 111, to deflect that air downwardly toward the pivotal connections 82, 85 and 86 of the rocker arm 81. Thus, the fine mist of lubricant in the air lubricates these rocker arm connections. Also, there are formed in the upper surface of counterweight 20 a numfines all of the air exhausted from the cylinder in a tained under compression between the forward enlarged portion 19 of rod 131 and a washer 137 bearing against the, forward end of wall 48 and spanning groove 135,

her of grooves 116 (see Fig. 8), which act to receive and collect a portion of the oil from the discharged air,

proximity of counterweight and its grooves 116 to vpivot pins 86 and 90 also of course will assure proper it is possible to place the air inlet passage 41 in communication with passage 42, forwardly of plug 118, so

More speso that spring 136 yieldingly urges rod 131 axially forwardly, to cause valve element 129 to seat against part 131}. When push button 19 is pressed rearwardly by the finger of a user, valve element 129 allows water or air to pass forwardly into seat member 130, and then downwardly through an opening in the bottom of that seat element and through a communicating passage 138 in section 11, to communicate with a tubular metal member 139 received within an enlarged diameter portion 140 of passage 138. This metal member 139 is brazed ,or otherwise secured to the previously mentioned tube 17 through which water or air is discharged onto the work surface. Tube 17 has an opening 141 communicating with passage 138, and through which the water or air enters tube 17. From the location of this opening v141, tube 17 extends laterally in opposite transverse di- The close 1 rections within a groove 142 formed in the undersurface 1 of portion 40 of section 11, and then the tube 17 curves downwardly at opposite sides of the sander (locations 143 in Fig. 6), to then curve forwardly at 144 (Fig. l) and extend along the bottom edges of the two side walls 37 of section 11' to the forward end of section 11. At

that forward end, the two ends 145 of tube 17 are bent that surface.

that air may be directed onto the work rather than water. For this purpose, a passage 119 extends transversely within rear portion 40 of handle section 11, to communicate with a vertical passage 120 extending upwardly to bore 42 (see Fig. 7). The bore 119 has an enlarged diameter portion 121, to form an annular valve seat at 122 engageable by a needle valve 123 which is threadedly connected at 124 into an outer mounting bore 125. A screw 126, sealed by a gasket 127, normally closes the outer end of threaded bore 125, but is removable to allow insertion of a screw driver into bore 125 into engagement with the screw driver slot 128 of needle valve element 123, to actuate the valve between opened and closed positions. When hose 18 is connected into bore 42, to supply water to bore 42, the needle valve 123 is closed to isolate bore 42 from the air supply inlet passage 41. However, when plug 118 is connected into passage 42, the needle valve 123 may be opened, to allow air from passage 41 to flow laterally through passage 119 and then upwardly through passage 120 into passage 42, to then follow the path normally followed by water for discharge onto the work surface.

The water or air in passage 42 flows forwardly past a manually actuable valve element 129 (see Fig. 2), which seats forwardly against the annular end of a hollow tubular seat element 130, stationarily positioned withinthe forward end of passage 42. Valve element 129 is actuable by an elongated horizontally extending push rod 131, whose enlarged forward end portion forms the previously mentioned push button 19 projecting forwardly through an opening 132 in the forward end of handle 11. As the rod 131 extends forwardly from its valve element 129, it may first extend through a transverse end wall of seat element 130, then an annularseal ring 133, then an opening 134 in handle element 11, following which rod 131 may extend forwardly through a groove 135 formed in the upper side of wall 48 Forwardly of, the wall 48 of handle section 11, 'a'coil spring 136 is disposed about rod 131, and is mainslightly downwardly, to open or face, and thus to direct the discharged water or air, essentially forwardly but slightly downwardly onto the work surface forwardly of. the pointof engagement of sanding paper 13 with Thus, these ends of tube 17 discharge the water or air'onto the work surface in alignment with the sand paper 13 and shoe 12 axially of the direction of reciprocation, so that the tool may be moved forwardly directly onto the portion of the surface which has been moistened or cleaned by the fluid discharged from tube 17.

The transverse portion of the tube 17 which is received within groove 142 (Fig. 6) is secured in the illustrated position within groove 142 by means. of a clamp 146, which may be tightened upwardly against the underside of portion 40 of section 11 by means of a screw 147, typical connected into the lower end of the previously mentioned passage (Fig. 7). Also, the forwardly extending horizontal portions of tube 17 received beneath the opposite side walls 37 of section 11 may be similarly secured to those side walls by a pair of clamps 148. The tube 139 (Fig. 6) secured to the upper side of tube 17 is so attached to the latter' as to prevent any leakage of fluid as fluid passes from tube 139 into tube 17. Also, leakage at the upper end of tube 139 may be prevented by tightening that tube upwardly against a deformable seal ring 149. p a

Fig. 9 represents a spring pressed assembly which may be provided for assisting valve element 99 in normally urging control member 16 upwardly to its valve closing position. Specifically this assembly of Fig. 9 may include a vertically movable push button element 150, which is confined within a passage 151 ,in Wall 48 for vertical movement, and is yieldingly urged upwardly by a coil spring 152, which is confined between element and the lower end of passage 151. The upper end of spring pressed element 150 bears upwardly against the upper side of element 16 to urg it upwardly to its Fig. 2 retracted position.

In describing the operation of the device, assume first that it is desired to use the device in a manner such that water will be discharged onto the work surface to assist in the sanding operation. In this case, the water supply line 18 is connected into passage 42, and the compressed air line 15 is connected into passage 41. Also, the lubricator 114 is connected into the air supply line, to feed a fine mist of oil into the compressed air. With the apparatus in this condition, a user may grasp handle 11 in his hand, and press downwardly against top element 16, to actuate valve 99'to its lower open position, and thus admit 2 compressed air to cylinder block 61 through passages 97, 104, 105 and 106. The slide valve 108 and pilot valve 208 will act to automatically control the supply of air to and the discharge of air from opposite ends of cylinder 61, to reciprocate piston 62 within the cylinder, and thus correspondingly reciprocate shoe 12 relative to handle 11. As the shoe reciprocates, the rocker arm 81 acts to reciprocate counterweight oppositely with respect to the shoe and relative to handle 11, so that there is little if any tendency to excessively move the handle itself.

The air discharged from cylinder 61 flows upwardly and then forwardly through passage 111, at the underside of deflector plate 114, and then leaves the forward end 112 of passage 111, to engage the down turned portion 116 of plate 114 and be deflected downwardly thereby. While the air is within the cylinder block 61, the lubricant mist acts to effectively lubricate valves 188 and 208 and piston 62. Also, after the air and lubricant are defiected downwardly by portion 116 of plate 114, the lubricant contacts the moving parts at pivots 82,85 and 86, and is received and accumulated within grooves 116 of counterweight 20, to continue lubrication of those pivots and of the pivot pins 88 and 90 at the rear end of the cylinder, so that proper lubrication of all of the moving parts of the counterweight mechanism is assured. When it is desired to discharge water onto the work surface, the user presses rearwardly on push button 19 (without moving the rest of his hand relative to handle 11), to thus openvalve 129 and allow water to flow past that valve into tube 17 for discharge forwardly from ends 145 of that tube onto the work surface at a location ahead of the sander. If, however, it is desired to discharge air onto the work surface forwardly of the sander, the hose 18 is detached from the device, and plug 118 is connected into passage 42, following which valve 123 is opened (this valve having been closed during discharge of water onto the work surface). In this condition, air may flow through passage 119 into passage 42, to then follow the same path previously followed by the water into tube 17 and out the forward ends 145 of that tube onto the work surface.

-I claim:

1. A sanding device comprising a handle adapted to be held in the hand of a user, a shoe carried by and reciprocable relative to said handle, means for attaching an abrasive sheet to said shoe for reciprocation therewith to abrade a work piece, compressed air actuated driving means for reciprocating said shoe relative to said handle, an inlet connection for compressed air flowing to said driving means, a conduit for discharging fluid onto a work surface adjacent said shoe and communicable with said air inlet for delivering air onto the work surface, a first valve for closing off communication between said air inlet and said conduit while still allowing air to flow to said driving means, a liquid inlet connection for connection to a supply of liquid when said first valve is closed, said liquid inlet connecton communicating with said conduit to then pass liquid therefrom onto the work through the conduit, a second valve operable to close off the discharge of either air or liquid through said conduit, and a third valve controlling the admission of air to said driving means.

2. A sanding device as recited in claim 1 including a plug for closing said liquid inlet when air is discharged through said conduit.

3. A sanding device comprising a handle adapted to be held in the hand of a user, a shoe carried by and reciprocable relative to said handle, means for attaching an abrasive sheet to said shoe for reciprocation therewith to abrade a work piece, a cylinder body attached to said handle, said shoe extending across the underside of said cylinder body, a piston in said body for actuating the shoe and having piston rods projecting in opposite axial directions therefrom, said shoe having a pair of upstanding projections received at the opposite ends of the cylinder respectively and against which said piston rods exert force to reciprocate the shoe with the piston relative to the handle, a counterweight at the underside of said cylinder body between said body and said shoe, a rocker arm near a first end of the cylinder body for reciprocating said counterweight reversely with respect to said shoe, means pivotally attaching said rocker arm at a first and upper location to an end portion of one of the piston rods at a first end of the cylinder body, means pivotally attaching said rocker arm at a second and lower location to the counterweight, and means attaching said rocker arm at a third and vertically intermediate location to said cylinder.

4. A sanding device as recited in claim ,3, including a link at the second end of the cylinder pivotally conhosted at its opposite ends to the cylinder and counterweight respectively to movably support the latter.

5. A sanding device comprising a handle adapted to be held in the hand of a user, a shoe carried by and reciprocable relative to said handle, means for attaching an abrasive sheet to said shoe for reciprocation therewith to abrade a work piece, powered means for reciprocating said shoe relative to said handle, an actuating element overlying said handle and manually depressible relative thereto, means operable by said actuating element to control the starting and stopping of said powered means, hinge means mounting said actuating element at one end to said handle, and a releasable leaf spring latch unit carried by said element at its other end and at its underside engageable upwardly against a shoulder on said handle to limit upward movement of the actuating element at a predetermined location but allowing limited upward movement for controlling said powered means, said leaf spring being deflectable to released position in which it can pass said shoulder to allow further upward movement of the actuating element, there being a space between said handle and said actuating element dimensioned to pass a screw driver downwardly past the said second end of said actuating element to contact and release said leaf spring.

6. A sanding device comprising a handle adapted to be held in the hand of a user, a shoe carried by and reciprocable relative to said handle, means for attaching an abrasive sheet to said shoe for reciprocation therewith H to abrade a work piece, an air operated piston and cylinder mechanism for reciprocating said shoe relative to said handle, an air inlet connection at a rear end of said handle communicating with said piston and cylinder;

' ing said first valve, a conduit for discharging water onto the work, a second valve for controlling the flow of water from said water inlet to said conduit, and a rearwardly movable finger actuated push button at the forward end of said handle movable independently of said actuating element and operable to actuate said second valve independently of said first valve, said air inlet connection being communicable with said conduit to discharge air therethrough, there being a third valve at the rear of said handle for closing off said communication between the air inlet and conduit.

References Cited in the file of this patent UNITED STATES PATENTS 1,954,489 Partlow Apr. 10, 1934 2,618,107 Martin Nov. 18, 1952 2,664,678 Wickes c- Ian. 5, 1954 2,825,188 Champayne Mar. 4, 1958 FOREIGN PATENTS 725,848 Great Britain Mar. 9, 19'55 

